Hetero-deformation and fracture of a near-eutectic high entropy alloy under dynamic impact

Abstract

Eutectic high entropy alloys (EHEAs) typically consist of two phases with distinct structures and properties, for example, soft and hard phases that deform heterogeneously. In this study, we report the deformation and failure phenomena in a near-EHEA (AlCoFeNi₂) with face-centered cubic (FCC) and ordered body-centered cubic (B2) phases under high strain rate impacts (up to ∼7 × 10³ s^-1). We find that such EHEA undergoes localized softening via the shear rupture of the brittle B2 phase, leading to high plastic strains at failures. Moreover, a majority of cracks initiate along cumulative wavy-slip traces within the B2 grains due to strain localizations. This study improves the understanding of the deformation and fracture mechanisms of EHEAs under dynamic impact conditions.